1. Field of the Invention
The invention relates to the production of adiponitrile from acrylonitrile by electrochemical synthesis, and particularly to an improvement in such a process wherein the electrodes are cleaned and replated in the electrohydrodimerization cell.
2. Background of the Invention
The reduction of acrylonitrile to adiponitrile by electrohydrodimerization is taught in British Pat. No. 1,089,707 (to Tomilov). In such a reaction, it is often preferred to use cathodic surface metals selected for high hydrogen over-voltage, and although metals such as lead, thallium, zinc, mercury and cadmium are preferred, because of the expense of the material and the lack of strength of these materials, it is common practice to electroplate the desired metal on a more suitable metal such as steel which is strong, readily available and inexpensive. A suitable cathode, for example, for the electrohydrodimerization of acrylonitrile to adiponitrile is cadmium-plated steel.
Electroplating of various metals by any of several methods, including the cyanide or alkaline method, the acid sulfate method, the pyrophosphate method, the fluoborate method and the phytic (hexaphosphoric) acid method, is well known. All are described, for example, in U.S. Pat. No. 2,973,308.
Commercially, electrolytic cells for electrochemical synthesis are constructed of electrodes in permanently fixed and substantial parallel planar relationship. Metal-plated cathodes are typically electroplated from cadmium sacrificial anodes.
In the course of electrohydrodimerization of acrylonitrile to adiponitrile, it is desirable, from time to time to clean and re-electroplate cathodes, and if such re-electroplating could be accomplished without disassembly of the electrode package and/or without removal of the package from the cell, a considerable amount of time and effort could be saved, such an accomplishment being a primary object of this invention.